Hi and welcome to LQ.
I've got a sneaking suspicion that you meant Red Hat Linux 9. I googled for "Lunux" (you know there are hundreds of distros these days) but I couldn't find anything specific.
If you mean Red Hat Linux 9, it's very old and unsupported. Please use a more modern version of Linux (eg. CentOS, Fedora, Slackware, Linux Mint, Ubuntu). Please note that technically speaking "Linux" is just a kernel, so there's no such a thing as Linux 9. The Linux kernel at the moment is something like 3.2.x. We usually talk about Linux Distributions, or Distros for short. The names I mentioned in the previous above are examples of Linux distributions.
By the way, what do you mean it won't let you enter one. If you're typing on a console, you will NOT see any characters being typed.